From c8dbde8dc8f6cabd5071151856aa945666661c42 Mon Sep 17 00:00:00 2001
From: Stevan Freeborn <65925598+StevanFreeborn@users.noreply.github.com>
Date: Sun, 29 Mar 2026 21:25:39 -0500
Subject: [PATCH] feat: support concurrency in json file storage provider

---
 .../Storage/JsonFileStorageProvider.cs        | 51 +++++++++++++++----
 .../Storage/JsonFileStorageProviderTests.cs   | 19 +++++++
 2 files changed, 61 insertions(+), 9 deletions(-)

diff --git a/src/StevanFreeborn.Extensions.Configuration.Secure/Storage/JsonFileStorageProvider.cs b/src/StevanFreeborn.Extensions.Configuration.Secure/Storage/JsonFileStorageProvider.cs
index 9fcb45f..8fd8482 100644
--- a/src/StevanFreeborn.Extensions.Configuration.Secure/Storage/JsonFileStorageProvider.cs
+++ b/src/StevanFreeborn.Extensions.Configuration.Secure/Storage/JsonFileStorageProvider.cs
@@ -4,6 +4,7 @@ namespace StevanFreeborn.Extensions.Configuration.Secure.Storage;
 
 public sealed class JsonFileStorageProvider(JsonStorageOptions options)
 {
+  private static readonly SemaphoreSlim FileLock = new(1, 1);
   private static readonly JsonSerializerOptions JsonOptions = new()
   {
     WriteIndented = true,
@@ -13,7 +14,7 @@ public sealed class JsonFileStorageProvider(JsonStorageOptions options)
 
   public async Task<string> ReadAsync(string key, CancellationToken ct = default)
   {
-    var data = await LoadAsync(ct);
+    var data = await LoadWithLockAsync(ct);
 
     if (data is not null && data.TryGetValue(key, out var v))
     {
@@ -25,22 +26,54 @@ public sealed class JsonFileStorageProvider(JsonStorageOptions options)
 
   public Task<Dictionary<string, string>> ReadAllAsync(CancellationToken ct = default)
   {
-    return LoadAsync(ct);
+    return LoadWithLockAsync(ct);
   }
 
   public async Task WriteAsync(string key, string encryptedData, CancellationToken ct = default)
   {
-    var data = await LoadAsync(ct);
-    data[key] = encryptedData;
-    await SaveAsync(data, ct);
+    await FileLock.WaitAsync(ct);
+
+    try
+    {
+      var data = await LoadAsync(ct);
+      data[key] = encryptedData;
+      await SaveAsync(data, ct);
+    }
+    finally
+    {
+      FileLock.Release();
+    }
   }
 
   public async Task<bool> DeleteAsync(string key, CancellationToken ct = default)
   {
-    var data = await LoadAsync(ct);
-    var result = data.Remove(key);
-    await SaveAsync(data, ct);
-    return result;
+    await FileLock.WaitAsync(ct);
+
+    try
+    {
+      var data = await LoadAsync(ct);
+      var result = data.Remove(key);
+      await SaveAsync(data, ct);
+      return result;
+    }
+    finally
+    {
+      FileLock.Release();
+    }
+  }
+
+  private async Task<Dictionary<string, string>> LoadWithLockAsync(CancellationToken ct)
+  {
+    await FileLock.WaitAsync(ct);
+
+    try
+    {
+      return await LoadAsync(ct);
+    }
+    finally
+    {
+      FileLock.Release();
+    }
   }
 
   private async Task<Dictionary<string, string>> LoadAsync(CancellationToken ct)
diff --git a/tests/StevanFreeborn.Extensions.Configuration.Secure.Tests/Unit/Storage/JsonFileStorageProviderTests.cs b/tests/StevanFreeborn.Extensions.Configuration.Secure.Tests/Unit/Storage/JsonFileStorageProviderTests.cs
index 69eac9f..922e827 100644
--- a/tests/StevanFreeborn.Extensions.Configuration.Secure.Tests/Unit/Storage/JsonFileStorageProviderTests.cs
+++ b/tests/StevanFreeborn.Extensions.Configuration.Secure.Tests/Unit/Storage/JsonFileStorageProviderTests.cs
@@ -79,4 +79,23 @@ public class JsonFileStorageProviderTests : IDisposable
 
     GC.SuppressFinalize(this);
   }
+
+  [Fact]
+  public async Task WriteAsync_WhenCalledConcurrently_ItShouldNotThrowFileInUseException()
+  {
+    const int numberOfWrites = 50;
+    var tasks = new List<Task>();
+
+    foreach (var index in Enumerable.Range(0, numberOfWrites))
+    {
+      tasks.Add(Task.Run(() => _sut.WriteAsync($"Key{index}", $"Val{index}")));
+    }
+
+    var act = async () => await Task.WhenAll(tasks);
+
+    await act.Should().NotThrowAsync();
+
+    var allData = await _sut.ReadAllAsync();
+    allData.Should().HaveCount(numberOfWrites);
+  }
 }
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